linux-kernel - [PATCH 2/2] usb: isp1760: Replace mdelay with msleep in isp1760

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Date:   Tue, 10 Apr 2018 15:37:06 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/2] usb: isp1760: Replace mdelay with msleep in isp1760_stop

isp1760_stop() is never called in atomic context.

The call chain ending up at isp1760_stop() is:
[1] isp1760_stop() <- isp1760_shutdown()

isp1760_shutdown() is set as ".shutdown" in struct hc_driver.
isp1760_stop() is also set as ".stop" in hc_driver.
These functions are not called in atomic context.

Despite never getting called from atomic context, isp1760_stop()
calls mdelay() to busily wait.
This is not necessary and can be replaced with msleep() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/usb/isp1760/isp1760-hcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/isp1760/isp1760-hcd.c b/drivers/usb/isp1760/isp1760-hcd.c
index 8e59e0c..5599310 100644
--- a/drivers/usb/isp1760/isp1760-hcd.c
+++ b/drivers/usb/isp1760/isp1760-hcd.c
@@ -2090,7 +2090,7 @@ static void isp1760_stop(struct usb_hcd *hcd)

 	isp1760_hub_control(hcd, ClearPortFeature, USB_PORT_FEAT_POWER,	1,
 			NULL, 0);
-	mdelay(20);
+	msleep(20);

 	spin_lock_irq(&priv->lock);
 	ehci_reset(hcd);
-- 
1.9.1